A serial dot matrix printer having a reciprocating print head that prints characters and so forth on paper has been known, as disclosed in U.S. Pat. No. 4,452,542. The actuator of the print head generates a considerable amount of heat when the head is in operation. For this reason, heat-dissipating fins are attached to the print head of the serial dot matrix printer to prevent the head from overheating.
As the head is moved, the heat-dissipating fins move through the surrounding air. Thus, the generated heat is dissipated through the fins. In general, the mechanism of the printer is housed in a casing and, therefore, the air confined in a space through which the head travels is stagnant. Accordingly, the capability of the known heat-dissipating fins to dissipate heat is insufficient, although the fins move in contact with air as the print head equipped with the fins moves. Consequently, if the printer prints characters at a high speed, e.g., 400 characters per second, the head overheats. The head incorporates a temperature sensor for detecting overheat so that the printing operation may be automatically halted when the head overheats. However, when the head of a high-speed printer is operated continuously for a considerable period, the temperature sensor operates frequently to interrupt the printing operation.
In the past, many components of a printer, including a carriage motor and a motor for shifting the carriage to a next line to be printed, were held in a frame made of a metal plate. Therefore, the heat produced by these motors could be dissipated through this metal frame. In recent years, however, as disclosed in Japanese Patent application No. 276304/1984, the frame of a printer has tended to be made from plastic. This structure presents the problem that the heat generated by the motors are difficult to dissipate. This problem is more conspicuous in high-speed printers, and may cause the motors to overheat and break down.